Add PowerPC 64-bit DWARF register mappings #390

Job	Run time
bench	1m 29s
Build fuzz targets	1m 28s
build (ubuntu-latest, stable)	45s
coverage	1m 4s
build (ubuntu-latest, beta)	54s
doc	28s
build (ubuntu-latest, nightly)	52s
cross (i686-unknown-linux-gnu)	51s
build (ubuntu-latest, 1.65.0)	3m 25s
features	2m 50s
cross (powerpc64-unknown-linux-gnu)	55s
build (stable, macOS-latest)	1m 10s
msrv-read	2m 40s
rustfmt	6s
Run `debug_abbrev` fuzz target	5m 6s
Run `debug_aranges` fuzz target	5m 9s
Run `debug_info` fuzz target	5m 10s
Run `debug_line` fuzz target	5m 7s
Run `eh_frame` fuzz target	5m 5s
Run `eh_frame_hdr` fuzz target	5m 6s
	49m 40s

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